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As many as 90 million American adults lack the reading and math skills needed to understand basic health information and navigate the U.S. health care system, according to a report issued Thursday by the Institute of Medicine.

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The report's authors stressed that the problem goes beyond the problem of low general literacy skills among adults, extending from persons who do not speak English as a first language to educated individuals who have a hard time interpreting complicated medical advice from doctors.

The IOM defines health literacy as the degree to which individuals have the capacity to obtain, process, and understand basic information and services needed to make appropriate decisions regarding their health.

The problem affects virtually all areas of American health care, from misleading food labels and drug information to overly complicated informed consent agreements, writing instructions, and government forms that prevent many people from accessing needed public health services, according to the report.

The study also calls on American doctors to improve the way they communicate with patients and asks medical schools to make better communication a part of regular student training.

"In health there's such a very high dependency on understanding," said IOM president Dr. Harvey Feinberg. "Every time there's a misunderstanding [between a doctor and a patient], there's a risk of life loss."

The report points to an increasingly complex health system that asks patients to decipher complicated information about multiple medications, surgical procedures, caloric intake, and a host of other issues. "These demands exceed the health literacy skills of most adults in the United States," it says.

Even those who read well have a hard time figuring out information from their insurers, doctors, or pharmacists, Dr. David A. Kindig, chair of the IOM panel, tells WebMD. "They're still confronting the health care system with all its complexity," says Kindig, a professor emeritus of population health sciences at the University of Wisconsin School of Medicine.

The problem was also highlighted last month when U.S. Health and Human Services Secretary Tommy G. Thompson announced that his department would ask food manufacturers to simplify food labels to help Americans make better dietary choices.

Limited data
The IOM panel reviewed 684 articles and studies looking at how low education levels and complex medical information affect health care in the U.S. Only a handful actually looked for direct links between poor health literacy and adverse medical outcomes.

One study showed that individuals with poor literacy skills had significantly more preventable hospital visits than those with higher skills. Another showed more unnecessary emergency room visits in the lower skills group.

Another study broadly estimated that low literacy skills cost the U.S. health care system $69 billion per year, though the information has not been confirmed, according to the report.

But experts said that they still do not know if there is a causal link between low literacy skills and poor medical outcomes, or if the possible link owes instead to socioeconomic conditions or ethnic differences. The report calls on the government to fund a broad program of research looking at the causes and consequences of low literacy on the health system.

"The problem we have is that most of this so far is anecdotal," says Dr. John C. Nelson, the president-elect of the American Medical Association.

Doctors can do more
The report also calls on medical schools to train physicians-to-be on how to better communicate with a broader range of patients. The AMA has launched an information kit for doctors nationwide urging them to simplify information for patients and to listen closely to patients' questions to see if they understand medical advice.

"If I tell you you've got hypertension, it doesn't mean nearly as much as 'you've got high blood pressure,'" Nelson says. "I was never taught as a physician how to do this," he explains.

IOM's report also says that few doctors have enough time in busy clinics to sit with patients long enough to make sure they understand advice.